Airconditioning generation system capable of solving unbalanced phase and method for the same

ABSTRACT

An airconditioning generation system capable of solving an unbalanced phase, and a method for solving the unbalanced phase are disclosed. The airconditioning generation system includes one or more indoor units ( 111, 112, 113, 121, 122, 131, 132, 133 ), one or more outdoor units ( 110, 120, 130 ), a generator ( 70 ) for providing the indoor and outdoor units with a power-supply signal, and a distribution unit ( 80, 80 ′) for detecting an individual-phase power value consumed by the indoor units, changing a phase of the power-supply signal transmitted from the generator ( 70 ) to the indoor or outdoor units, and establishing three-phase equilibrium. Therefore, if an unbalanced phase occurs in the three-phase power-supply signals applied to an airconditioner, the system solves the unbalanced phase, such that it prevents a product from being damaged and increases product reliability.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an airconditioning generation system capable of solving an unbalanced phase and a method for the same, and more particularly to an airconditioning generation system capable of solving an unbalanced phase and a method for the same, which can prevent the occurrence of an unbalanced phase of a power-supply signal applied to a plurality of outdoor units connected to a plurality of indoor units due to a difference in load.

2. Description of the Related Art

It is necessary for a driving power-supply signal to drive electrical devices for use in households or factories. Generally, the above-mentioned electrical devices have been designed to receive necessary power-supply signals from a commercial power source provided from the Korea Electric Power Corporation (KEPCO).

However, if a plurality of indoor units and a plurality of outdoor units are installed in households or factories, it may be difficult for the commercial power-supply signal received from an external part to be sufficiently applied to all driving loads of the indoor and outdoor units, such that a large number of households or factories may frequently use additional self-generation systems, respectively.

FIG. 1 is a structural diagram illustrating a conventional airconditioning generation system.

Referring to FIG. 1, the airconditioning generation system includes a plurality of indoor units 11, 12, 13, 21, 22, 31, 32, and 33 installed in individual rooms to cool or heat air in the rooms; a plurality of outdoor units 10, 20, and 30 connected to individual indoor units; and a generator 40 for generating a three-phase power-supply signal, and providing the outdoor units 10, 20, and 30 with the three-phase power-supply signal.

The airconditioning generation system further includes a molded-case circuit breaker 50 for detecting current values of individual phases of the three-phase power-supply signal generated from the generator 40, and preventing individual outdoor units 10, 20, and 30 from being powered on when an unbalanced phase occurs in the three-phase power-supply signal.

Although the outdoor units 10, 20, and 30 may be driven by the three-phase power-supply signal generated from the generator 40, the indoor units 11, 12, 13, 21, 22, 31, 32, and 33 are driven by a single-phase power-supply signal, such that the indoor units 11, 12, 13, 21, 22, 31, 32, and 33 are connected to a single-phase power-supply terminal from among individual power-supply terminals of the outdoor units 10, 20, and 30, and then receive a necessary power-supply signal via the single-phase power-supply terminal.

If an unbalanced phase occurs in a power-supply signal applied to the outdoor units 10, 20, and 30 due to a difference in driving load of indoor units connected to the outdoor units 10, 20, and 30, the molded-case circuit breaker 50 connected to the generator 40 prevents the power-supply signal from being applied to individual outdoor units 10, 20, and 30.

In other words, the airconditioning generation system acts as a three-phase four-line system, receives a three-phase power-supply signal composed of an R-phase power-supply signal, an S-phase power-supply signal, and a T-phase power-supply signal, and includes a neural(N)-line connected to the R/S/T-phase power-supply signals. The R-phase power-supply signal, the S-phase power-supply signal, and the T-phase power-supply signal have a phase difference of 120°, and establish phase equilibrium therebetween.

In this case, the R/S/T-phase power-supply signals generally establish the above-mentioned phase equilibrium, such that a current signal is not applied to the N line. However, if loads connected to individual phase power-supply signals have different magnitudes, there is an unexpected difference in an amount of a current signal applied to individual phase power-supply signals, such that the above-mentioned phase equilibrium is broken, and the current signal flows in the N line.

The above-mentioned state is called an unbalanced phase state. If the current signal flows in the N line as described above, a potential of the N line is increased such that a controller for controlling the airconditioning generation system may malfunction.

If an excessive current signal flows in a one-phase line or a two-phase line due to the unbalanced phase, a compressor contained in each of the generator, the indoor units, and the outdoor units is overheated, such that the compressor may be damaged or a microprocessor of the generator 40 may incur a malfunction or a faulty operation, resulting in the occurrence of a malfunction of the airconditioning generation system, and endurance deterioration thereof.

The molded-case circuit breaker 50 detects the value of a current signal flowing in the N line using an internal sensor. If the molded-case circuit breaker 50 detects the value of the current signal, it determines the occurrence of an unbalanced phase, such that it blocks a power-supply signal from being transmitted from the generator 40 to individual outdoor units 10, 20, and 30.

The molded-case circuit breaker 50 for use in the above-mentioned conventional airconditioning generation system generally aims to protect the generator 40 from danger, such that it immediately blocks a power-supply signal from being applied to all of the indoor and outdoor units if an unbalanced phase occurs by one of the outdoor units.

Therefore, if the power-supply signal is not applied to the indoor and outdoor units, a user must manually adjust individual loads of the indoor units 11, 12, 13, 21, 22, 31, 32, and 33, or the outdoor units 10, 20, and 30 to remove the unbalanced phase. The user cannot use the above-mentioned airconditioning generation system at all locations of a building or factory equipped with the system until the unbalanced phase is removed, resulting in greater inconvenience of the user and reduction of product reliability.

SUMMARY OF THE INVENTION

Therefore, the present invention has been made in view of the above problems, and it is an object of the invention to provide an airconditioning generation system capable of solving an unbalanced phase and a method for the same, which can prevent the occurrence of an unbalanced phase in a generation system capable of providing an airconditioner with a three-phase power-supply signal, such that they prevent the occurrence of a malfunction or damage of a manufactured product due to the unbalanced phase, and increase product reliability.

It is another object of the invention to provide an air-conditioning generation system for greatly increasing its power factor and a method for the same, which detect an amount of a current signal applied to individual airconditioners to prevent the occurrence of an unbalanced phase, determine the presence or absence of the unbalanced phase, and change power-supply wiring arrangement of individual airconditioners according to the determined result associated with the unbalanced phase.

In accordance with one aspect of the present invention, these objects are accomplished by providing an airconditioning generation system capable of solving an unbalanced phase, comprising: a plurality of indoor units; and a plurality of outdoor units, wherein power values of individual-phase driving power-supply signals consumed by the indoor and outdoor units are summed, and a power-supply wiring structure of some parts of the indoor and outdoor units is automatically changed to another wiring structure when there is a difference in power consumption values of individual phases, resulting in three-phase equilibrium.

Preferably, the distribution unit includes: a sensor for detecting a current signal flowing in a wiring structure which receives the power-supply signal from the generator and transmits the received power-supply signal to the indoor and outdoor units; and a distribution controller for calculating the sum of individual-phase power consumption of the indoor and outdoor units according to the output current value of the sensor, and changing the wiring structure to another wiring structure when there is a difference in the sum of the individual-phase power consumption.

Preferably, the distribution unit includes: a communication unit for communicating with the outdoor units, and receiving power consumption data of the indoor and outdoor units from the outdoor units; and a distribution controller for calculating the sum of individual-phase power consumption of the indoor and outdoor units, and changing a wiring structure capable of transmitting a power-supply signal from the generator to the indoor and outdoor units when there is a difference in the sum of the individual-phase power consumption.

In accordance with another aspect of the present invention, there is provided a method for solving an unbalanced phase in an airconditioning generation system, comprising the steps of: a) calculating power consumption of indoor and outdoor units; b) calculating the sum of the calculated power consumption values to determine the presence or absence of the unbalanced phase; and c) changing a wiring structure of a power-supply signal supplied to the indoor or outdoor units when the presence of the unbalanced phase is determined.

The airconditioning generation system includes a distribution unit capable of detecting individual-phase power values consumed by the indoor units, and changing a wiring structure of a phase power-supply signal transmitted from the generator to the outdoor units. If the unbalanced phase occurs in the three-phase power-supply signal, the airconditioning generation system automatically solves the unbalanced phase, such that it prevents a product from being damaged, and increases product reliability.

Also, if the unbalanced phase occurs in the three-phase power-supply signal, the airconditioning generation system changes a wiring structure of individual-phase power-supply signals to establish three-phase equilibrium, improves power factor, such that it reduces power consumption of an overall system and costs thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects, and other features and advantages of the present invention will become more apparent after reading the following detailed description when taken in conjunction with the drawings, in which:

FIG. 1 is a structural diagram illustrating a conventional airconditioning generation system;

FIG. 2 is a structural diagram illustrating an airconditioning generation system in accordance with a first preferred embodiment of the present invention;

FIG. 3 is a flow chart illustrating a method for operating the airconditioning generation system shown in FIG. 2 in accordance with the first preferred embodiment of the present invention;

FIG. 4 is a structural diagram illustrating an airconditioning generation system in accordance with a second preferred embodiment of the present invention; and

FIG. 5 is a flow chart illustrating a method for operating the airconditioning generation system shown in FIG. 4 in accordance with the second preferred embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, preferred embodiments of the present invention will be described in detail with reference to the annexed drawings. In the drawings, the same or similar elements are denoted by the same reference numerals even though they are depicted in different drawings. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

For example, an airconditioning generation system capable of solving an unbalanced phase according to the present invention includes 3 outdoor units and 8 indoor units, but it is not limited to this example, and is applicable to other examples without limiting the number of outdoor or indoor units connected to a generator.

FIG. 2 is a structural diagram illustrating an airconditioning generation system in accordance with a first preferred embodiment of the present invention.

Referring to FIG. 2, the airconditioning generation system in accordance with the first preferred embodiment of the present invention includes 8 indoor units 111, 112, 113, 121, 122, 131, 132, and 133; 3 outdoor units 110, 120, and 130 connected to the eight indoor units 111, 112, 113, 121, 122, 131, 132, and 133; a generator 70 for generating a drive power-supply signal of the indoor and outdoor units by driving an engine; and a distribution unit 80 for dividing a three-phase power-supply signal generated from the generator 70 into individual phase signals, and providing the outdoor or indoor units with the divided phase signals.

The airconditioning generation system may further include a molded-case circuit breaker 90 connected to the generator 70 and the distribution unit 80. If an unbalanced phase occurs irrespective of operations of the distribution unit 80, the molded-case circuit breaker 90 blocks individual outdoor units 110, 120, and 130 from receiving a power-supply signal.

In this case, the first outdoor unit 110 is connected to three indoor units 111, 112, and 113, the second outdoor unit 120 is connected to two indoor units 121 and 122, and the third outdoor unit 130 is connected to three indoor units 131 and 132, such that they adjust an amount of a refrigerant flowing in individual indoor units.

The three-phase power-supply signal generated from the generator 70 is divided into R-, S-, and T-phase signals via the distribution unit 80, and is applied to individual outdoor units 110, 120, and 130. Individual outdoor units transmit the R/S/T-phase power-supply signals to individual indoor units.

In the meantime, the generator 70 may be implemented with a general three-phase voltage generator capable of providing the indoor units 111, 112, 113, 121, 122, 131, 132, and 133 and the outdoor units 110, 120, and 130 with a power-supply signal. For example, a cogeneration system may be used as the generator 70.

The cogeneration system generates electricity using a cogeneration generator, and uses waste heat of the cogeneration generator. The cogeneration system includes an engine, and a cogeneration generator for generating power using rotating force of the engine, and further includes a heat provider. The heat provider receives either waste heat of a cooling water of the engine or other waste heat of discharge gas of the engine, and transmits the received heat to a target such as an airconditioner.

Also, the power generated from the cogeneration generator is used to operate a variety of electric devices such as an electric lamp, and an airconditioner, etc. The heat provider receives waste heat of the cooling water of the engine or other waste heat of discharge gas of the engine, such that it performs a hot-water supply operation using the received waste heat or provides the airconditioner with the received waste heat.

The distribution unit 80 includes a distribution controller 82, which divides the three-phase power-supply signal received from the generator 70 into individual phase signals, transmits the divided phase signals to the outdoor units 110, 120, and 130 and the indoor units 111, 112, 113, 121, 122, 131, 132, and 133, and controls a wiring board to which the three-phase power-supply signal or a single-phase power-supply signal is applied.

The distribution unit 80 further includes a sensor 81 for detecting the value of a current signal flowing in the wiring structure capable of providing the indoor and outdoor units with a power-supply signal, such that the distribution controller 82 controls the wiring structure according to the output value of the sensor 81.

The distribution controller 82 receives the value of a current signal supplied to individual indoor units 111, 112, 113, 121, 122, 131, 132, and 133 and individual outdoor units 110, 120, and 130 from the sensor 81, and calculates the value of a power signal consumed by the indoor and outdoor units in individual phase signals according to the received current value, and controls the wiring structure to establish phase equilibrium in individual phase signals according to the calculated power value.

FIG. 3 is a flow chart illustrating a method for solving an unbalanced phase of the airconditioning generation system in accordance with the first preferred embodiment of the present invention. The method for solving the unbalanced phase of the airconditioning generation system will hereinafter be described with reference to FIG. 3.

Referring to FIG. 3, an engine of the generator 70 is driven to generate a power-supply signal at step S1.

The power-supply signal is transmitted to the distribution unit 80 connected to the generator 70, and is supplied to the outdoor units. The power-supply signal is divided into individual phase signals, such that it is supplied to the indoor units as a single-phase power-supply signal.

The distribution unit 80 detects the value of a current signal of the power-supply signal transmitted to individual indoor and outdoor units using the sensor 81, calculates the value of consumed power on the basis of the detected current value, and sums the calculated power value in individual phases at step S2.

For example, provided that each of the indoor units 111, 112, 113, 121, 122, 131, 132, and 133 connected to the outdoor units 110, 120, and 130 consumes predetermined power of 5HP, and each outdoor unit consumes predetermined power of 10HP, power consumed by the first outdoor unit 110 and the indoor units 111, 112, and 113 connected to the first outdoor unit 110 is an R-phase signal having a predetermined power value of 25HP, power consumed by the second outdoor unit 120 and the indoor units 121, 122, and 123 connected to the second outdoor unit 120 is an S-phase signal having a predetermined power value of 20HP, power consumed by the third outdoor unit 130 and the indoor units 131, 132, and 133 connected to the third outdoor unit 130 is a T-phase signal having a predetermined power value of 25HP.

In this case, the distribution unit 80 detects the value of a current signal of a wiring board receiving the R/S/T-phase power-supply signals, such that it can determine how much R/S/T-phase power-supply signals are supplied to individual indoor and outdoor units in the same manner as in the above-mentioned power consumption calculation method.

If there is a difference in the sum of power consumption of individual phases, the distribution controller determines the occurrence of the unbalanced phase, and calculates an amount of power to be consumed by individual phase power-supply signals to establish phase equilibrium at steps S3˜S5.

A wiring structure of some parts of the indoor or outdoor units is changed according to the amount of the calculated power to establish the phase equilibrium at step S6.

Therefore, if the R-phase signal consumes the power of 25HP, the S-phase signal consumes the power of 20HP, and the T-phase signal consumes the power of 25HP according to the calculated power consumption of individual phases, the power consumed by the S-phase signal is relatively less than those of the R-phase and T-phase signals, resulting in the occurrence of an unbalanced phase. Each of the R/S/T-phase signals must consume power of 70HP/3 to establish the phase equilibrium, such that a wiring structure is controlled to provide the first and third outdoor units with the S-phase power-supply signal suitable for the power of 70HP/3.

Also, the distribution unit 80 repeatedly checks load of individual phases after the phase equilibrium is maintained, and changes the wiring structure to establish the phase equilibrium.

An airconditioning generation system according to a second preferred embodiment of the present invention does not mount the sensor to the distribution unit, and calculates the value of power consumption of individual phases by allowing the distribution unit to communicate with the outdoor units, differently from the above-mentioned airconditioning generation system according to the first preferred embodiment in which the sensor is mounted to the distribution unit.

FIG. 4 is a structural diagram illustrating the airconditioning generation system in accordance with a second preferred embodiment of the present invention.

Referring to FIG. 4, a plurality of indoor units 111, 112, 113, 121, 122, 131, 132, and 133 are connected to outdoor units 10, 20, and 30, and communicate with the outdoor units 10, 20, and 30, such that information associated with power consumption or load are communicated between the indoor units and the outdoor units.

In this case, the indoor units are connected to the outdoor units via a cable, and communicate with the outdoor units according to an RS-485 communication scheme or a power-line communication scheme, such that a variety of wired/wireless communication schemes can be established between the indoor units and the outdoor units to implement an object of the present invention.

The distribution unit 80′ divides a three-phase power-supply signal generated from the generator 70 into individual phase signals, and transmits the divided phase signals to the indoor and outdoor units. The distribution unit 80′ includes a communication unit 83 communicating with the outdoor units 110, 120, and 130, and a distribution controller 82′ for determining the presence or absence of an unbalanced phase on the basis of transmission/reception data of the communication unit 83, and changing a wiring structure according to the determined result associated with the unbalanced phase.

In the meantime, if the airconditioning system composed of the indoor and outdoor units includes a plurality of outdoor units, at least one outdoor unit is determined to be a master, and the remaining outdoor units are determined to be slaves, such that the slave outdoor units can be centrally controlled according to operation commands of the master outdoor unit. According to the second preferred embodiment of the present invention, the first outdoor unit 110 is determined to be the master outdoor unit, and the second and third outdoor units 120 and 130 are determined to be the slave outdoor units.

In this case, the indoor unit 111 is connected to the outdoor unit 110 according to an RS-485 communication scheme, communicates with the outdoor unit 110, and is controlled by the outdoor unit 110. Other indoor units are connected to the indoor unit 111 and the outdoor unit 110 according to the RS-485 communication scheme, and are controlled by the master outdoor unit 110.

FIG. 5 is a flow chart illustrating a method for solving an unbalanced phase of the airconditioning generation system shown in FIG. 4 in accordance with the second preferred embodiment of the present invention.

Referring to FIG. 5, an engine of a generator is driven to generate a power-supply signal.

The power-supply signal is transmitted to a distribution unit connected to the generator, and is supplied to the outdoor units. Also, the power-supply signal is divided into individual phase signals, such that it is supplied to indoor units as a single-phase power-supply signal at step S11.

Individual indoor units or slave outdoor units communicate with a master outdoor unit, and transmits their power consumption data to the master outdoor unit at step S12.

The distribution unit communicates with the master outdoor unit, such that it receives power consumption data of individual indoor and outdoor units. The distribution unit reads the power consumption data, and recognizes the value of power of a three-phase or single-phase power-supply signal consumed by individual indoor and outdoor units at step S13.

The power values recognized in individual phases are summed, and the magnitudes of the power values are compared with each other, such that the presence or absence of an unbalanced phase can be determined according to the comparison result at step S14.

If the occurrence of the unbalanced phase is determined, the distribution unit changes a wiring structure of the outdoor units or some parts of the outdoor units according to the calculated power value in the same manner as in the first preferred embodiment of the present invention, such that phase equilibrium can be established at steps S15˜S16.

The distribution unit repeatedly checks load of individual phases after the phase equilibrium is maintained, and changes a wiring structure to establish the phase equilibrium.

In the same manner as in the first preferred embodiment, provided that power consumption of the R-phase signal is 25HP, power consumption of the S-phase signal is 20HP, and power consumption of the T-phase signal is 25HP, a wiring structure for providing the outdoor units with a power-supply signal is changed to another wiring structure in which power of 70HP/3 is consumed by individual phase signals. For example, the S-phase power-supply signal designed to provide the second outdoor unit with a power-supply signal is also applied to the first and third outdoor units, such that power consumption of the S-phase power-supply signal is increased and at the same time other power consumption of the R/T-phase power-supply signals is reduced, resulting in phase equilibrium in three phases.

As apparent from the above description, an airconditioning generation system and method capable of solving an unbalanced phase includes: one or more indoor units; one or more outdoor units for providing the indoor units with a single-phase power-supply signal; a generator for providing the outdoor units with a power-supply signal; and a distribution unit for checking individual-phase power values consumed by the indoor units, changing a phase of the power-supply signal transmitted from the generator to the outdoor units according to the checked power values, and establishing phase equilibrium in three phases. Therefore, if the unbalanced phase of a three-phase power-supply signal occurs when the power-supply signal is supplied to an airconditioner, the present invention solves the unbalanced phase, such that it prevents a product from being damaged and increases product reliability.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. 

1. An airconditioning generation system capable of solving an unbalanced phase, comprising: a plurality of indoor units; and a plurality of outdoor units, wherein power values of individual-phase driving power-supply signals consumed by the indoor and outdoor units are summed, and a power-supply wiring structure of some parts of the indoor and outdoor units is automatically changed to another wiring structure when there is a difference in power consumption values of individual phases, resulting in three-phase equilibrium.
 2. An airconditioning generation system capable of solving an unbalanced phase, comprising: an airconditioning system including one or more indoor units and one or more outdoor units; a generator for providing the airconditioning system with a driving power-supply signal; and a distribution unit for detecting power values of individual-phase driving power-supply signals of the airconditioning system, changing some parts of phases of the power-supply signal transmitted from the generator to the airconditioning system, and establishing three-phase equilibrium.
 3. The airconditioning generation system according to claim 2, wherein the outdoor units are driven by a three-phase power-supply signal.
 4. The airconditioning generation system according to claim 2, wherein the indoor units are driven by a single-phase power-supply signal.
 5. The airconditioning generation system according to claim 2, wherein the distribution unit includes: a sensor for detecting a current signal flowing in a wiring structure which receives the power-supply signal from the generator and transmits the received power-supply signal to the indoor and outdoor units; and a distribution controller for calculating the sum of individual-phase power consumption of the indoor and outdoor units according to the output current value of the sensor, and changing the wiring structure to another wiring structure when there is a difference in the sum of the individual-phase power consumption.
 6. The airconditioning generation system according to claim 5, wherein the distribution controller changes a wiring structure when there is a difference in individual-phase power consumption, such that a phase power-supply signal having less power consumption is additionally connected to other outdoor or indoor units.
 7. An airconditioning generation system capable of solving an unbalanced phase, comprising: an airconditioning system including one or more indoor units and one or more outdoor units; a generator for providing the airconditioning system with a driving power-supply signal; and a distribution unit for receiving operation data of the indoor units from the outdoor units, calculating power consumption of the indoor and outdoor units on the basis of the received operation data, changing a wiring structure of a phase power-supply signal supplied to the airconditioning system, and establishing three-phase equilibrium.
 8. The airconditioning generation system according to claim 7, wherein the distribution unit includes: a communication unit for communicating with the outdoor units, and receiving power consumption data of the indoor and outdoor units from the outdoor units; and a distribution controller for calculating the sum of individual-phase power consumption of the indoor and outdoor units, and changing a wiring structure capable of transmitting a power-supply signal from the generator to the indoor and outdoor units when there is a difference in the sum of the individual-phase power consumption.
 9. The airconditioning generation system according to claim 7, wherein the distribution controller changes the wiring structure when there is a difference in individual-phase power consumption according to the sum of power consumption of the indoor and outdoor units, such that a phase power-supply signal having less power consumption is additionally connected to other outdoor or indoor units.
 10. The airconditioning generation system according to claim 1 or 2, wherein the generator is a cogeneration generator.
 11. A method for solving an unbalanced phase in an airconditioning generation system, comprising the steps of: a) calculating power consumption of indoor and outdoor units; b) calculating the sum of the calculated power consumption values to determine the presence or absence of the unbalanced phase; and c) changing a wiring structure of a power-supply signal supplied to the indoor or outdoor units when the presence of the unbalanced phase is determined.
 12. The method according to claim 11, wherein the step a) includes the steps of: a1) detecting a value of a current signal transmitted from a generator to the outdoor and indoor units; and a2) calculating power consumption of individual outdoor unit and indoor units on the basis of the detected current value.
 13. The method according to claim 11, wherein the step a) includes the steps of: a3) transmitting data associated with power consumption in a predetermined range from the indoor units to the outdoor units; and a4) calculating a value of power consumption of individual indoor and outdoor units on the basis of the power consumption data received from the outdoor units.
 14. The method according to claim 11, further comprising the steps of: allowing a generator to generate a three-phase power-supply signal before performing the step a); and dividing the three-phase power-supply signal generated from the generator into three single-phase power-supply signals, and providing the outdoor units with the single-phase power-supply signals.
 15. The method according to claim 11, wherein the step b) includes the steps of: b1) summing power consumption of the indoor and outdoor units in individual phases; and b2) determining the occurrence of the unbalanced phase if there is a difference in power consumption of individual-phase power-supply signals.
 16. The method according to claim 15, wherein the step c) includes the step of: if the presence of the unbalanced phase is determined at the step b), changing the wiring structure in which a phase power-supply signal having less power consumption is supplied to other indoor units.
 17. The method according to claim 11, further comprising the step of: repeating the above steps until the unbalanced phase of the three-phase power-supply signal is solved. 